60 GHz and 45 GHz wireless communications fall in the category of millimeter wave communications. A millimeter wave refers to an electromagnetic wave at a frequency of 300 GHz to 30 GHz and with a wavelength of 1 to 10 mm, and is widely applied to many fields such as communications, radar, navigation, remote sensing, and radio astronomy. As an important branch of millimeter wave communications, the 60 GHz and 45 GHz communications have the following advantages.
Large channel capacity. Bandwidth of 60 GHz and 45 GHz frequency bands is a relatively large license-free frequency band. License-free bandwidth exceeding 5 GHz enables a 60 GHz technology to have great potential in capacity and flexibility, and enables the 60 GHz technology to have a Gbit-level wireless application prospect. In addition, spectrum management allows the 60 GHz technology to have much larger transmit power than other existing wireless local area network (WLAN) and wireless personal area network communication technologies (WPAN), so that a path loss of the 60 GHz frequency band can be overcome.
Good directivity, and strong security and confidentiality. Under a same antenna size, the millimeter wave has a much narrower beam than a microwave. Therefore, 60 GHz and 45 GHz radio waves have good directivity, and fit well for point-to-point short range communications.
Good international adaptability. Countries such as European countries, the United States, and Japan specify in succession continuous license-free spectrum resources within a range of 57 GHz to 66 GHz. Spectra of the countries are allocated to bandwidth nearby 60 GHz, where there is a common frequency of about 5 GHz. Therefore, 60 GHz wireless communications products have good international adaptability.
60 GHz and 45 GHz wireless communications technologies can provide transmission at a multi-gigabit rate to support high-definition video transmission, fast synchronization, a wireless USB, and a high-speed wireless local area network.
A wireless local area network may be a basic service set (BSS) including a wireless access device, or may be a BSS including no wireless access device (un-infrastructure BSS). The wireless local area network generally includes a network controller and a station. The network controller provides, by using a directional multi-gigabit beacon frame (DMG Beacon) or an announcement frame, a station with a channel access period allocation service, such as a service period (SP) and a contention-based access period (CBAP). Different from a conventional 802.11 Beacon frame, the DMG Beacon frame is dedicated to BSSs at the 60 GHz and 45 GHz frequency bands, and has functions such as network synchronization, beamforming training, and SP and CBAP allocation. In the BSS, time is generally divided into time intervals with a beacon interval (BI) as a period, where each BI includes some channel access periods. Referring to FIG. 1, which is a schematic diagram of access periods within a BI, a beacon transmission interval (BTI) is a transmission interval of a DMG Beacon directional multi-gigabit beacon frame. Association beamforming training (A-BET) is a beamforming training period when association is performed between the network controller and a newly accessed station. An announcement transmission interval (ATI) is a request/answer-based round-robin management access period between the network controller and the station. A data transfer interval (DTI) is a data sending period, where the DTI is divided into any combination of CBAP and SP time periods by means of scheduling by the network controller, the CBAP is a contention-based access period, and the SP is a dedicated service period.
When allocating the SP and the CBAP within the DTI, the network controller needs to perform scheduling to avoid interference. Because a beamforming-based directional transmission technology is used, 802.11ad allows overlapping between different SPs allocated to different stations within a BSS. An overlapped SP can improve spatial sharing and multiplexing within the BSS. However, when a reserved SP overlaps with another SP, the reserved SP may be interfered by an adjacent BSS or a current BSS. Interference can be avoided by establishing a guard period for an SP.
However, in the prior art, it is required that a station of an SP needs to establish a guard period only in a case in which a network controller joins a centralized cluster. If the network controller does not join a centralized cluster, the station of the SP itself determines whether to establish a guard period for the SP, but the station of the SP cannot effectively determine when the guard period should be established. As a result, protection overheads increase due to blind establishment of guard periods, and interference is caused when no guard period is established due to missing scheduling information of an adjacent BSS.